Multiple anatomical landmark calibration for optimal bone pose estimation

Angelo Cappello, Aurelio Cappozzo, Pier Francesco La Palombara, Luigi Lucchetti, Alberto Leardini

Research output: Contribution to journalArticlepeer-review


Bone motion estimation by means of photogrammetric, non-invasive methods can be severely corrupted by experimental errors. The largest fraction of such errors is associated with the relative movement between externally located markers and the underlying bone, due to the interposition of both passive and active soft tissues. The errors affecting the estimates of anatomical landmarks trajectories in the laboratory frame can be considerably reduced by following the Calibrated Anatomical System Technique protocol which entails: (i) a static calibration of the anatomical landmarks in a technical reference frame defined by the cluster of skin markers, and (ii) the use of a rigid model of the cluster. This paper illustrates how a modification of the above-mentioned protocol, involving a multiple calibration of the anatomical landmarks in different postures, and the use of a deformable model of the cluster, can effectively enhance bone motion estimation. In order to validate the new protocol a cycling test on a patient wearing a femoral external fixator was performed. The root mean square reconstruction error (RMSE) on an anatomical landmark (greater trochanter) trajectory drops from over 15 mm to less than 10 mm while the RMSEs of the bone (femur) orientation and position decrease respectively from about 5 deg and 7 mm with our previous protocol to less than 4 deg and 4.5 mm. The improvements are even more significant when movement components relative to the main planes and axes of motion are considered.

Original languageEnglish
Pages (from-to)259-274
Number of pages16
JournalHuman Movement Science
Issue number2-3
Publication statusPublished - Apr 1997


  • Bone pose estimation
  • Human movement
  • Multiple calibration
  • Skin artefact
  • Three-dimensional analysis

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Experimental and Cognitive Psychology
  • Neuropsychology and Physiological Psychology
  • Human Factors and Ergonomics


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